Lubricating oil



'ing metals, etc.

2,359,088 LUBRICATING on.

Paul R. Van Ess, Berkeley, Oalifl, assignor to Shell Development Company, San

Francisco, Calif a corporation of Delaware No Drawing. Application September 23, 1941,

SerialNo. 411,972

17 Claims.

This invention reiates to improved lubricating oils, and more particularly is concerned with compounded mineral lubricating oils to which have been added, small amounts of certain organic arsine disulfides.

It is already known that the presence of various sulfur and arsenic compounds in lubricating oils may exert beneficial influences. Thus sulfur compounds have been added in order to increase the load-carrying capacity of the oil, or to retard corrosion toward certain alloy bear- Arsenic compounds have been used to improve oiliness, to retard corrosion and to reduce wear. a

The effect of sulfur in particular as an anticorrosive has been in the past a subject of considerable investigation, and it has been found that different sulfur compounds'are' widely different in their effect. Many sulfur compounds, such as thiophenes, are wholly ineflective.

(CL 252i-33) Others are so extremely active that they frequently induce corrosion, particularly to ferrous metals. For example, free sulfur, H28 or compounds readily liberating S or H28, while protecting certain alloys, are very dangerous, particularly when used in the lubrication of internal combustion engines. It thus appears that the sulfur in the compound must possess an activity toward bearing metals above a certain minimum in order to display its protective effect, and, on the other hand, it must not be so active as to cause corrosion to ferrous metals.

The problem of relative corrosiveness or anticorroslveness of various compounds is further complicated by the fact that lubricating oils containing them are used over wide temperature ranges and under hydrolyzing and/or oxidizing to dissolve more than .1 to .2% without danger of precipitating at least a portion thereof.

It is a purpose of this invention to produce a lubricating oil suitable for internal combustion engines which is non-corrosive to bearing metals over the entire normal temperature range of internal combustion engines. It is another purpose to produce a compounded non-corrosive lubricating oil containing dissolved a detergent which under normal lubricating conditions may induce corrosion and in addition a relatively large amount of an arsine sulfide. purpose is to produce a lubricant which materially reduces wear under hydrolyzing and/or oxidizing conditions. Still another purpose is to produce a lubricating oil containing an arsenic compound which is easy to manufacture, is readily soluble in hydrocarbon oils in quantities above about .1%, is substantially nonvolatile and which, even at elevated tempera.- tures, does not have the repulsive odor possessed by many organic arsenic compounds. 1 I have discovered that lubricating oils to which have been added small amounts of organic arsine disulfides possessing the formula RAsSz wherein R is a hydrocarbon radical having at conditions. In the past, the influence of these factors has not been sufilciently taken into consideration, and therefore much of the information available is contradictory and misleading.

The ideal anti-corrosion compound is one which is readily soluble in hydrocarbon oils and which over a wide temperature range, i. e., from about normal room temperature up to about 200 C. (the highest-crank case temperature likely ever to be encountered) is sufilciently.

active to prevent or retard corrosion of bearing metals, and, on the other hand, is not so active as to attack ferrous metals within the same temperature range.

Amon the many additives for lubricating oils is triphenyl arsine sulfide which, although useful, unfortunately has a limited solubility in lubricating oils, it being, in general, impossible least 4 carbon atoms, have the desired anticorrosive properties for bearing alloys over the entire normal crankcase temperature range and over prolonged operating conditions, as may occur in internal combustion engines. The arsine disulfides of this invention are oil-soluble in useful quantities, stable and non-volatile, and the sulfur in them does not attack ferrous metals even at elevated temperatures. p

The hydrocarbon radical may be aliphatic, alicyclic or aliphatic substituted aromatic, aliphatic chains being preferred, particularly those having 10 or more carbon atoms, for reasons discussed later. It may contain polar substitution radicals provided that they do not unduly limit the oil-solubility of the compound. Thus it may contain hydroxyl, ether, sulfide, amino, imino, halogen, etc., radicals.

Suitable unsubstituted hydrocarbon radicals are, for example, butyi, isobutyl, tertiary butyl,

A further suppress corrosion vary normally between about 0.05-2% and preferably between 03-05%.

A is known, compounds of certain elements,

relatively low melting point of the alloy, thehigh spot melts away and fills in minute depressions, thereby causing an effective polishing of the bearing surface without the use of an abrasive. On the perfectly smooth bearing'surface, the load i more evenly distributed which results in more perfect fluid lubrication and reduces the wear. The presence of certain polar compounds having long carbon. chains further enhances the wear reduction by forming wedges between the gliding metal surfaces.

It has been shown, however, that certain disturbing influences may completely destroy any advantages that may possibly be gained by the addition of "chemical polishing compounds." For example, under conditions favoring corrosion, the polishing may be oflset by the corrosion, newly formed high spots being continuously formed which are then melted down. As a result, the rate of wear may increase rather than decrease. Such has been found to be the case, for example, with tricresyl phosphate which, when tested in the so-called four-ball machine (described in Engineering, vol. 136 (1938) p. 46) proves to be an excellent anti-@wear agent, but in an internal combustion engine actually increases wear. In the latter case, apparently, traces of phosphoric acids are liberated, probably due to hydrolysis, which traces are responsible for corrosion resulting in increased wear by the mechanism explained above.

Moreover, the formation of the alloy inthe polishing mechanism requires that the alloyforming element can be liberated at the proper moment. Oxidized compounds of the elements must first be reduced before the element can be freed, and it was found that for this reason, in general, oxidized compounds are poorer polishing agents than non-.oxidized ones. For example, an arsine is a better polishing compound than an arsenite or arsenate.

Arsine disulildes in which the organic radical contains arsenic, hydrocarbon chains of 10- or more carbon atoms have the advantage of being able to produce the'wedging efiect mentioned earlier, thereby further reducing wear. Thus these compounds combine the three properties of highly effective corrosion protection under a wide range of conditions, eflective chemical polishing and wear-reducing due to wedging eflect.

The arsine disulildes of this invention are particularly useful for the purpose of suppressing the corrosiveness of lubricating oils containing added small amounts of detergents, e. g., from .25%-5% alcohol having at least 4 carbon atoms in the 7 s,sso,osa i W p presence of air to accordance with the formula: A82l+RR+JO=2RA8OI produce an arsine dioxidein is bubbled. Arsine disulilde is precipitated as a pasty or oily mass which is' separated and dried. The dry product is readily soluble in hydrocarbon oils.

The following examples riirtlier illustrate my invention:

EXAIPLI I 55 V. I. lubricating oil 8. A. E. 30 grade was divided into two portions. To one portion was added 1.25% by weight of calcium petroleum suli'onate. This doped portion was subdivided into two portions and to one of these portions was added .2% of normal butyl arsine disulnde.

The doped and undoped oils were then tested by a test known-as the Thrust bearing corrosion test, which is carried out as follows: A hardened steel disc is made to rotate'for 20 hours under constant pressure against three flat copper-lead bearings. The bearing assembly rests in a steel cup filled with the oil to be tested, and the temperature of the oil maintained at a predetermined figure by thermostatic control. The bearings are weighed before and after the test, the difference in weight representing the loss sustained during the test.' The tests were run with the same bearings and oil until the end of the last recorded period. Intermediate bearing losses were determined by removing, cleaning, and weighing the Bearin wgt. loss in rngJsq.

cm. at 120 C.

Additive m 30 2nd so hours hours None... .2 Calcium petroleum l7. 6

sulionate.

overheated because of excessive corrosion and rouglleulng.

B. A. E.30 Calcium petroleum 0.1.

sullonate+.l% nbutyl-arslne disulilde.

The test results of Table I indicate that the corrosivityof the calcium petroleum sulfonate has been substantially eliminated by the butyl arsine disulilde.

' Exusrns II Avoltolized oil was prepared by subiectinga rapeseed oil having a viscosity of 236 S. U. Secs. at F.and60.5 S. U. Secs. at 210 1". (V. I. 154) to silent electrical dkcharges for4 hours at 210 F., at which time it possessed the following characteristics: Viscosity 3402 S. U. Secs. at 100 F. and 392 S. U. Secs; at 210 F., and V. I. 128. To a 50 V. I. lubricatlng oil,'S. A. E. 30 grade, was added 9% by" weight of this voltolized rapeseed oil. This dope was subdivided into two portions and to one of these portions was added. .l% by weight of normal butyl arsine disulflde. The doped and undoped oils were then tested in a Lauson engine, which is a 4-cycle, L-head vertical single cylinder engine. Oil is circulated through the engine by a pump which takes suction on an oil reservoir.

. The crankcase oil temperature of 100 C. is controlled by a strip heater mounted under the crankcase. The jacket temperature is maintained at 140 C. by an evaporative cooling system. The engine is run at 1700 R. P. M. for 30 hours. New copper-lead bearing shells are placed in the connecting rod before each test.

Results were as follows:

Table II EXAMPLE 111 A 55 V. I. lubricating oil, S. A. E. 30 grade, containing 1.25% of calcium petroleum sulfonate was run in 9. Caterpillar Diesel engine for 60 hours. The oil was too corrosive at this stage .to be tested high molecular weight hydrocarbon polymer having detergent properties and a small amount of an arsine disulfide having the formula RASSc, wherein R is a hydrocarbon radical having at least 4 aliphatic carbon atoms.

'4. A non-corrosive mineral lubricating oil containing a corrosion-inducing amount of a voltolized oleaginous substance and a small amount of an arsine disulfide having the formula RASS2, wherein R is a hydrocarbon radical having at least 4 aliphatic carbon atoms.

8. A non-corrosive mineral lubricating oil containing a corrosion-inducing amount of a voltolized rapeseed oil and a small amount of an arsine disulfide having the formula RASSa, wherein R. is a hydrocarbon radical having at least 4 aliphatic carbon atoms.

9. The composition of claim 1, wherein the arsine disulfide is normal butyl arsine disulfide.

10. A method of lubricating alloy bearings of the group consisting of copper and lead alloy bearings in internal combustion engines which by the Thrust bearing corrosion test, described in Example I. .2% by weight of n-butyl arsine disulfide was added to the used oil and this dopedused oil subjected to the Thrust bearing corrosion test at 107 C. for 20 hours, using copper-lead bearings.- The bearings tested in the doped-used oil showed no measurable loss of weight, indicating the corrosivity of the oil was substantially completely overcome by the addition of the nbutyl arsine disulfide.

I claim as my invention:

1. A non-corrosive lubricating oil comprising a predominant amount of a mineral lubricating oil containing dissolved a small amount of an oilsoluble arsine disulfide having the formula RAsSz, wherein R. is a hydrocarbon radical having at least 4 aliphatic carbon atoms.

2. A non-corrosive lubricating oil comprising a predominant amount of a mineral lubricating oil containing dissolved a small amount of an oilsoluble arsine disulflde having the formula RAsSz, wherein R is an aliphatic hydrocarbon radical having at least 10 carbon atoms.

3. A non-corrosive lubricating oil comprising a predominant amount of a mineral lubricating oil containing dissolved between ODS-2% of an oil-soluble arsine disulfide having the formula RAsSz, wherelnR is a hydrocarbon radical having at least 4 aliphatic carbon atoms.

4. A non-corrosive mineral lubricating 011 containing an added oil-soluble detergent normally causing corrosion and-a small amount of. an arsine disulflde having the formula RASSa,

wherein R is a hydrocarbon radical having at least 4 aliphatic carbon atoms the amount of said .method consists in applying to the bearing surfaces a non-corrosive compounded lubricating oil comprising a predominant amount of a mineral lubricating oil whicn contains (1) an amount of an oil-soluble detergent normally suiiicient to impart corrosive properties to said 011 and (2) an amount of an oil-soluble arsine disuliide having the formula RAsbz wherein R. is a hydrocarbon radical having at least 4 aliphatic carbon atoms, which amount of arsine disulnde is sumcient to render said corrosive oil substantially non-corrosive.

11. The method of claim 10 wherein the detergent is calcium petroleum suli'onate."

12. The method of claim 10 wherein the detergent is calcium petroleum sulfonate and the disulfide is n-butyl arsine disulfide.

13. A method of lubricating alloy bearings of the group consisting of copper and lead alloy bearings in internal combustion engines which method consists in applying to the bearing surfaces the composition of claim 1, thereby inhibiting corrosion of the bearing surface.

14. A method of lubricating alloy bearings of the group consisting of copper and lead alloy bearings in internal combustion engines which method consists in applying to the bearing surbearings ininternal combustion engines which method consists in applying to the bearing sirfaces the composition of claim 6, thereby inhibiting corrosion of the bearing surface.

16. A method of lubricating alloy bearings of the group consisting of copper and lead alloy hearings; in internal combustion engines which method consists in applying to the bearing surfaces the composition of claim 7, thereby inhibiting corrosion of the bearing surface.

17. A method of lubricating alloy bearings of the group consisting of copper and lead alloy bearings in internal combustion engines which method consists in applying to the bearing surfaces the composition of claim 8, thereby inhibiting corrosion of the bearing surface.

PAUL R. VAN ESS. 

